Alloy steel article



Patented Nov. 26, 1940 UNITED STATES ALLOY STEEL ARTICLE Vsevolod Nicholas Krivobok, Pittsburgh, Pa., as-

signor to Rustless Iron and Steel Corporation, a

corporation of Delaware Original application June 25, 1935,

No Drawing.

Serial No. 28,376. Divided and this application October 19, 1937, Serial No. 169,907

1 Claim.

This application is a division of my copending application 28,376 filed June 25, 1935 and entitled Alloy and manufactures, now Patent 2,125,- 299 of August 2, 1938, and this invention relates to chromium-nickel alloy irons and steels and to articles and manufactures of the same,

One of the objects of my invention is the provision of high-grade alloy irons and-steels, which are strong, tough and durable and which lend themselves to a variety of working and forming operations into a great number of tubular articles, products and manufactures, which are peculiarly adapted .to high temperature duty for long periods of constant use under a wide variety of corrosive or corrosion-fostering media.

Another object is the production of alloy irons and steels of the character described which lend themselves to simple, direct and economical working, as by forging, upsetting and hot and cold so rolling into bar, rod, sheet and strip stock, which lend themselves to a number of working and forming operations, such as drilling, cutting, threading or other machining or bending, pressing, punching, or blanking, to achieve many commercial-tubular articles and manufactures.

Another object of my invention is the production of alloy irons and steels of the character indicated, which lend themselves to ready fabrication as by welding into various tubes and pipes as used in oil cracking stills, condensers, boilers and the like in a number of chemical industries.

The invention accordingly consists in the combination of elements, composition of ingredients and mixture of materials, and in the articles, products and manufactures of the same, as described herein, the scope of the application of which is indicated in the following claim.

As conducive to a clearer understanding of certainfeatures of my invention it may be noted at this point that the austenitic chromium-nickel irons and steels containing approximately, 10% to 25% chromium, 7% to 15% nickel, and the balance substan-tially'iron, are used in the production of a wide variety of corrosion-resistant and mildly heat-resistant products or articles of manufacture. These austenitic irons and steels, especially the 18-8 irons and steels containing approximately, 18% chromium, 8% nickel, and the balance substantially iron, are used in a number of interior or exterior architectural applications, such as decorative trim, ornamentation and fixtures. Similarly, these irons and steels are employed for a variety of kitchen, soda fountain, dairy and hospital applications, as in cooking and serving utensils, containers and appliances,

counter and furniture trim and the like, where permanently bright corrosion-resistant metal capable of withstanding the corrosive action of various vegetable and fruit acids, is desired. Likewise, these irons and steels are widely adapted for various chemical plant apparatus and equipment where metal resistant to the corrosive attack of acids, alkalies and salts at room temperature, or slightly elevated temperature, is required.

These austenitic chromium-nickel irons, and steels, however, are not especially adapted for extremely high temperature duty, particularly high temperature duty understrongly oxidizing or corrosive conditions, or conditions of friction, abrasion and wear, largely because of the susceptibility of these irons and steels to intergranular corrosion.

One of the outstanding objects of my invention is the production of strong, tough and durable chromium-nickel alloy irons and steels, which are especially resistant to grain growth and embrittlement, scaling, pitting and intergranular corrosion, wear and abrasion, all at high temperatures, which may be worked or formed into a variety of tubular articles, products and manufactures, and which are adapted to reliably withstand long periods of continuous high temperature high pressure duty under the many varying conditions of shock, vibration, wash and scour of fluids, corrosive attack and the like, as encountered in actual, practical use. v

As illustrative of the practice of my invention, chromium-nickel alloy iron orsteel analysing approximately, 18% chromium, 8% nickel, 2.5% to 3.5% tungsten, .5% to 1% titanium, .07% to .1% carbon, and the balance substantially iron, with the usual percentages of manganese, silicon, sulphur and phosphorus, is conveniently produced in an electric furnace in any suitable manher, as described in Patent No. 1,925,182 granted ,September 5, 1933 to Alexander L. Feild and entitled Process for the manufacture of rustless iron. The alloy iron or steel is poured into suitable ingot molds where it is permitted to cool fully retain the high strength, hardness and other physical properties imparted by the cold working operation.

My modified chromium-nickel alloy iron or steel is essentially austenitic in structure but contains certain new constituents in the form of complex ferrites and carbides. The metal, when made up into articles of the character noted, is resistant to the corrosive eflects of various industrial gases, vapors, fumes, liquids, acid, alkaline or salt in character, and is resistant to grain growth and embrittlement, pitting, scaling and intergranular corrosion and is highly resistant to impact, shock and fatigue under high temperature operating conditions over long periods of constant use. For example, a bar of my alloy iron or steel analyzing approximately, 18% chromium, 8% nickel, 3% tungsten, .3% titanium, 10% carbon and the balance substantially iron, has a life of about 350 hours under stress of 8,000 pounds per square inch at a temperature maintained at 1500 F. under ordinary atmospheric conditions. Under like operating conditions the usual 18-8 chromium-nickel iron analyzing approximately, 18% chromium, 8% nickel, .07% carbon, and the balance substantially iron, has a life of about 12 hours.

My alloy iron or steel in addition to having a life under severe operating conditions of high tensile stress at high temperatures in the presence of a variety of corrosive or corrosion-fostering agents, greatly in excess of heretofore known and/or used austenitic chromium-nickel alloy irons and steels, is strong, tough and durable and lends itself to a variety of working and forming operations. The metal may be upset. Likewise, the metal lends itself to a variety of hot and cold working or forming operations, either from sheet, strip or bar stock, such as punching, bending, and the like. In addition, the metal may be cut, drilled, turned, threaded and otherwise machined to desired specification. Furthermore, the metal may be readily welded using the oxy-acetylene torch or the electric arc (employing welding rods for the electric welding operation of approximately the same analysis as the stock welded). In the production of welded parts, articles or manufactures, these are preferably heat-treated in accordance with well known methods. after the welding operation is completed, in order to establish a stable structure and assure maximum chemical resistance and minimum embrittlement, intergranular corrosion and other deterioration in actual, practical use.

My modified chromium-nickel alloy iron or steel readily lends itself to the production of a great many tubular articles, products and manufactures of commerce, such as welded tubes, fluid valves, and couplings, all for high temperature duty, as in boilers, condensers, oil cracking stills, evaporator units and the like, for semi-chemical use in the canning, dairy, oil and photographic film industries, or for chemical calciners, as used in the production of iron-free chemicals, such as paints and dyes. In addition, my chromiumnickel alloy iron or steel may be worked or formed, as above indicated, achieving a further variety of high temperature duty articles, parts and accessories, possessing great resistance to wear and erosion, in addition to strength, toughness, resistance to shock, corrosion-resistance under high temperature operating conditions where the wash and scour of hot corrosive or corrosion-fostering gases are encountered.

Thus, it will be seen that there is provided in this invention modified chromium-nickel alloy irons and steels and especially tubular articles, products and manufactures of the same, in which the various objects hereinbefore noted, together with many thoroughly practical advantages, are successfully achieved. It will be seen that the alloy irons and steels are strong, tough and durable, corrosion-resistant, heat-resistant and resistant to grain growth and fatigue and furthermore that the irons or steels are readily workable into a variety of tubular articles, products and manufactures, which are especially adapted to withstand continuous high temperature duty over long periods of time and under the many varying conditions encountered in actual, practical use.

While as illustrative of my invention, modified chromium-nickel alloy irons and steels, and articles, products and manufactures thereof, containing approximately, 18% chromium, 8% nickel, 2.5% to 3.5% tungsten, .3% to 1% titanium, 07% to .l% carbon, and the balance substantially iron, are specifically described above, it will be understood that good results are achieved where the chromium content ranges between 10% and 25% and the nickel content between 7% and Likewise, high temperature duty chromium-nickel alloy irons and steels of good heat resisting and corrosion resisting characteristics, in combination with good mechanical workability, are achieved where the tungsten content ranges from just above 2% up to about 4%, the titanium from- .30% up to about 1.5%, and the carbon content ranging from about 03% up to about 20%. A somewhat higher carbon content is permissable in the irons and steels of the higher chromium and nickel contents although it is to be understood that the presence of carbon is not desired but is present only because it is commercially impracticable to rid the metal of this ingredient.

Modified chromium-nickel alloy irons and steel of especially good resistance to the corrosive attack of sulphur-bearing agents, such as hydrogen sulphide, are achieved by a supplementary addition of manganese in the amount of from about .5% to 3%. The presence of a fairly high percentage of manganese in the metal greatly facilitates the production of the alloy irons or steels in that it increases the fluidity of the molten metal. Furthermore, manganese measurably improves certain working and forming characteristics of these irons and steels.

As many possible embodiments may be made of my invention and as many changes may be made in the embodiment hereinbefore set forth, it is to be understood that all matter described herein is to be interpreted as illustrative, and not in a limiting sense.

I claim:

Wrought alloy austenitic 10 to per cent chromium, 7 to 15 per cent nickel, and .03 to .20 per cent carbon, stainless steel tubular articles characterized by their freedom from corrosion embrittlement and by their resistance to the wash and scour of corrosive fiuids, used under conditions of high internal pressures and at high temperatures, said characteristics being produced by the inclusion in said alloy steel of .3 to 1.5 per cent titanium, and over 2 per cent up to 4 per cent tungsten.

VSEVOLOD NICHOLAS KRIVOBOK. 

